The present invention relates to folded telescoped mast drilling rigs. More particularly, the present invention relates to a method and apparatus for erecting a folded lower mast and a telescoped upper mast to elevated operating positions on a drill platform, locking the upper mast to a transfer frame, and moving the transfer frame to a position to align upper and lower guide rails for the power swivel and to transfer the load of the upper mast to the lower mast support structure.
Various folded or telescoped mast drilling rigs may be used in either land or ocean based drilling operations. For desert or other land operations, the folded mast may be supported from a trailer truck for transporting the rig to the drill site. Typically, the folded mast section extends from its pivot point above the rear portion of the trailer towards the front end of the trailer.
There are various systems which may be employed to erect a lower mast and a pivotally connected upper mast to a vertical position. Hydraulic rams are commonly used to unfold the lower and upper masts together. In other systems a line reeved through sheaves on the mast sections connect to a drawworks which winds the line on a cable reel. Pulling the line pulls the mast into an erect operating position.
U.S. Pat. No. 3,295,270 issued to Woolslayer, et al. describes a two-section folded oil well mast structure. The back sides of the two sections hinge together permitting the upper mast to fold over the lower mast. In this apparatus the mast structure erects into a vertical operating position by winding a line onto a drawworks cable reel. The line extends along the lower mast and over the pivot hinge to a traveling block near the pivot point. A hook on the traveling block connects to a sling which connects between the lower and the upper mast sections. Winding the line on a cable reel moves the travelling block towards the front of the mast. The hook pulls on the fixed sling to swing the mast sections to an erect position.
U.S. Pat. No. 4,134,237 issued to Armstrong describes a modular section mast having telescoped modular mast sections which are inserted at remote land sites or on an offshore platform by a small capacity crane into the open side of the U-shaped lower mast. The uper mast is inserted and raised by cable in the erect lower mast. The intermediate mast is inserted and secured to the lower end of the upper mast. Removable retainer plates guide the upper and intermediate mast sections within the lower mast when being extended by pulling on a pulling line. After the mast is fully erected, the structures are bolted together.
U.S. Pat. No. 4,393,630 issued to Knox describes a truck mounted telescoping well mast structure which pivotally connects at its lower end to a truck. The mast structure folds over the truck from its pivotal connection at the rear of the truck. In raising the mast, the lower mast structure pivots from a horizontal position to a vertical position. The upper telescope structure then slides or moves upwardly on bearing pads permitting reciprocal travel of the upper structure relative to the lower structure. The upper mast may be extended and retracted by a hydraulic cylinder. A trolly having wheels moves along the inside edge of a vertical member of the lower mast section. The trolly is secured within a housing at the upper end of the lower section by an elongated track connected to the upper section. Securing the trolly locks a cable to allow the racking platform to extend.
U.S. Pat. No. 2,804,948 issued to Woolslayer, et al. describes a telescoping portable mast having two sections. The lower end of the mast is hinged so that the mast may swing to a horizontal reclining position. The legs of the upper mast have tongues which insert axially into forks on the lower mast. The legs then rigidly connect by splice pins. The legs of the lower section serve as guide rails for grooved wheels to support and guide the upper section when it extends or retracts.
U.S. Pat. No. 2,804,949 issued to Woolslayer, et al. describes a two-section telescoping portable mast hinged at its lower end to enable a mast to swing to a substantially horizontal position. The legs of the upper mast have tongues which insert axially into forks on the lower mast. The legs are rigidly connected by splice pins. A trolly roller suspended from the top of the lower section engages a rail extending longitudinally along the upper section. The roller and rail cooperate to guide the extension and retraction of the upper mast.
While folded and telescoped masts provide mobility and stability during transportation, these masts must be secured to withstnad the stresses of the mast. During drilling operations, the frame members for the mast sections must be aligned and secured by pinning or other means to transmit the loading on the mast to the mast support structure.
U.S. Pat. No. 2,336,432 issued to Wilson describes a two-section telescoped oil well mast having corner angle members that are aligned axially. These members laterally support and guide the upper mast section. After the telescoped mast is fully extended, the adjacent portions of the upper and lower mast sections are wedged together to secure the upper mast to the lower mast. It is of concern, however, that this wedging and locking is not able to withstand a significant backlash from the drilling operation. In that situation, the upper and lower sections of the mast may separate causing destruction of the mast and dangerous operating conditions for the drillers.
Some of these folded and telescoped masts also do not appear adapted to advantageously employ a power swivel for turning the drill string. The present invention enables a compact drill rig mast to use a power swivel for drilling operations. The power swivel is a relatively recent advance in drilling technology. Dolly wheels connected to the power swivel housing run on a pair of flanged guide rails to resist torque and to keep the power swivel aligned with the well centerline. Use of guide rails permits more rapid vertical movement of the traveling block which is suspended from the drawworks cable. A drill rig using a folded or a telescoped mast and a power swivel would have to align the power swivel guide rail in the various mast sections to permit drilling activity.